With reference to FIG. 1, a typical construction of a gasoline fuel injector, generally indicated at 10, includes a valve body 12, in which a valve seat 14 is hermetically secured via a weld 16. The valve seat 14 has multiple functions such as to provide 1) a guide for the armature tube ball assembly, generally indicated at 18, 2) a conical sealing surface on which the ball 20 sits, and 3) orifice holes for spray generation.
The valve seat 14 is a machined and ground part and is fixed to the valve body 12 via the hermitic weld 16 through the valve body wall and into the valve seat 14. During this operation, the material that was molten during the weld process shrinks during cooling causing distortion of the seat 14.
The distortion imposed on the critical areas of the seat 14 can be modeled through a displacement in the weld area. In a simulation, a four micron uniform displacement in the weld area was shown to result in an equivalent or greater displacement in the guide and seal area of the seat 14. It is noted that distortion by welding is not uniform and the resulting distortion of the seat 14 is thus also not uniform. This distortion of the seat 14 results in leaks at the seal and non-uniform shrinkage of the guide portion of the seat 14, which cause durability problems of the fuel injector 10.
Thus, there is a need to provide an improved fuel injector seat that resists distortion during welding upon assembly.